The revelation comes just days after it emerged that almost £1.2m was paid to three prosecution barristers in the case, which ended in the acquittal of the accused Sean Hoey after a 56 day trial.

But the total cost of the trial is likely to continue to increase as final bills have yet to be tallied.

A spokeswoman for the Legal Services Commission told the Telegraph that the total it has paid to date is £2,425,958, which includes fees to legal representatives, VAT and payments made by solicitors on behalf of a client.

She said that criminal legal aid certificates are issued by the court and at the conclusion of cases such as this the legal representatives submit a claim to the Taxing Master.

The spokeswoman added: “The Taxing Master completes an assessment and determination of amounts to be paid. The Taxing Master notifies the Legal Services Commission and the Commission makes payment.

“No final determination of the amounts to be paid has been made or notified to the Commission, which is accordingly not able to provide any information regarding the final costs. Payments have however been issued by the Commission in respect of interim payments claimed.”

SDLP justice spokesman Alban Maginness said he is “very concerned at this large expenditure of public funds.”

Mr Maginness added: “I think the whole thing is a terrible waste of money. There should be a cap on fees paid in all cases that are brought. Until the government and legal bodies here get together to discuss this it is an open market here. The Assembly is not helping by not meeting and discussing issues like this. We have people saying lets just get on with it and someone will pay and that someone is usually the tax payer.”

Alliance leader David Ford however said that the trial cost should not be criticised as the people of Omagh deserve justice.

He added: “People should not forget that this atrocity saw the single biggest loss throughout the whole troubles. Such criticisms are unfair and do not take into account the trauma endured by victims, survivors and families affected by the bombing.”

The Omagh Bomb trial is one of three high-profile and expensive prosecution cases to fail.

The most recent was the collapse of the trial of bank employee Chris Ward who was accused of stealing £26.5m from the Northern Bank. And earlier this year Terence Davison was acquitted of the murder of Belfast man Robert McCartney.

The Telegraph has learned that to date £31,416 in legal aid has been paid to defence lawyers in the case against Terence Davison and £243,333 to prosecution barristers. More than £56,000 in legal aid has so far been paid to defence lawyers in the case of Christopher Ward who was acquitted of the Northern Bank robbery. The prosecution costs in the Northern Bank case are not yet known as they have yet to be paid to the PPS.